On the Trilobite Genus Celmus Angelin, 1854 By Valdar Jaanusson ABSTRACT.-The trilobite species Ceimus granUtatus ANGELIN, 1854 is redescribed. Following FR. ScHMIDT (1907) the genus Crotalurus VoLBORTH, 1858, is considered as a junior subjec­ tive synonym of Celmus ANGELIN, 1854· A new family Celmidae is erected with Celmus as the sole representative. The terms eu-ptychopariid and steno-ptychopariid type of ventraJ cephalic sutures are introduced to denote a broad and a narrow rostraJ shield, respectively, separated by sutures. A new subfamily Mesotaphrasinae is erected for certain genera with levisellid type of facial suture including Mesotaphrasis, Chomatopyge and, provisionally, Clelandia. In 1854 ANGELIN (pp. 23-24, PI. XVII, fig. 8-8 a) erected a new trilobite genus and species narned Celmus granulatus derived from strata regianis C, Skarpåsen, Östergötland. He illustrated and briefly described the cephalon and thorax whereas the pygidium was apparently unknown to him. The genus was left unplaced in family. In 1858 VoLBORTH (pp. 126-133, PI. XII, fig. 1-5) described a trilobite from the Lower Ordavieian limestones at Pavlovsk, Ingermanland, believing it to represent a new genus and species which he narned Crotalurus bar­ randei. His thorough description comprised the whole carapace with the exception of the hypostoma. The genus was left unplaced in family. As far as can be judged from the references in his paper the monograph of Angelin (1854) had not been available to him. The genus Crotalurus was included in the family no. XV (Cheiruridae) by BARRANDE (1872, p. XXX). FR. ScHMIDT (1881, pp. I 19-120) excluded it, however, from the Cheiruridae on account of its opisthoparian facial suture hut left open the taxonomical position of this genus. Subsequently FR. ScHMIDT (1907, pp. IS-I6, PI. I, figs. 9, 10, u ) published a redescrip­ tion of VoLBORTH's material of Crotalurus barrandei VoLB. From a study of photographs of the type specimens of Celmus granulatus he conducled that Celmus and Crotalurus are subjective synonyms, and that also the type species of these genera appear to be synonymous. Nevertheless, he continued to use VoLBORTH's name for the genus and species painting out that VoL­ BORTH's description was more complete, and that the generic name Crotalurus had been more widely used in the literature than Celmus. In this paper 3-553271 Bull. of Geol. Vol. XXXVI VALDAR JAANUSSON FR. ScHMIDT again included Crotalurus tentatively in Cheiruridae chiefly because no better place for this genus could be found ( cf. also STUBBLEFIELD I936, p. 4I6). WEBER (I932, pp. I22-I23) included Crotalurus in Proetidae on account of the general resemblance of the glabella in Crotalurus and Cyphaspis. He also described the new species Crotalurus? strigatus from Tamdy River, Karatau Range, bu t pointed out in a footnote (p. I22, foot­ note I) that this species no doubt belongs to Glaphurina erected by ULRICH (I930) in a paper which became accessible to WEBER first after his manu­ script had already been submitted for publication. ÖPIK (I937, p. 92) sug­ gested that Celmus (incl. Crotalurus) should probably be placed into a new opisthoparian family. Recently TJERNVIK (I952, pp. 6I, 64) recorded Crotalurus n. sp. from the Lower Planilimbata limestone of Närke, and BOHLIN (I955, p. II5) Celmus granulatus from the Raniceps limestone of Öland, and (I955, pp. I27-I28) Celmus aff. granulatus from the Gigas limestone of Öland. In connection with the preparation of the trilobite part of the Treatise of Invertebrate Paleontology it appeared necessary to settie the taxonornie position of the genus Celmus. For this purpose the present writer undertook a study of all available material of Celmus from Sweden, including the cotypes of ANGELIN. In the present paper a rede8cription of the type species of Celmus is given tagether with a discussion on the taxonornie position of the genus. The pygidium, previously unknown from Sweden, and the hypos­ toma, hitherto not known in this genus, are also included in the description. The material studied belongs to the following museums: State Museum of the Natural History (Naturhistoriska Riksmuseet) in Stockholm (RM), Museum of the GeologicaJ Survey of Sweden (SGU), and Museum of the Palaeontologieal Institution of the Univ. of Uppsala (UM). Remarks on the Terminology In the literature on trilobites written in English language the middle region of thorax and pygidium is frequently termed "axis", and the furrows which limit this region laterally-the "axial furrows". These terms have been u sed by SALTER (I 864, etc.) who was followed in this respect by WARBCRG (I925) in her critical revision of the terminology of the trilobite carapaee. The fact that WARBURG herself in her later papers ( e.g. I939, p. 6) found these terms to be inadequate and replaced them by the old terms "raehis" and "dorsal furrow" is, however, less known. The word "axis" means a line and its use for an area of a body is not quite happy. The term "axial lobe" u sed by WALCOTT (I 908 and later p apers) is a more suitable term if the use of the word "axis" for the middle region of the trilobite Clrapaee is preferred. For this region DALMAN (I 827) had introdueed the term "rhachis" (in English usually "raehis") and as this paper of DALMAN may be regarded as the foundation of the scientific terminology of the ON THE TRILOBITE GENUS CELMUS ANGELIN, 1854 37 trilobite carapace, his terms may reasonably be retained. The term "axial furrow" in the sence of "sulcus dorsalis" of DALMAN (1827) is, however, from the point of view of zoological terminology, entirely misleading and ought to be dropped. DALMAN's term "dorsal furrow" has been widely accepted (e.g. BARRANDE 1852 ["sillon dorsaux"], RrcHTER 1912 ["Riicken­ furche"], WARBURG 1939, Howeli et al. 1947, to mention only a few out­ standing discussions on the terminology of the trilobite carapace), and is used also in the present paper. For brevity as well as darity symbols have been used in the present paper to denote the lateral glabellar lobes and furrows. The present writer completely agrees with WARBUR G (1939, p. 5) in considering unnatmal the numbering of glabellar furrows and lobes from behind forwards. On the other hand, as pointed out by several writers (most recently by WHITTING­ TON & EviTT 1954, p. 13), this method of numbering provides at present the only possibility assigning the same figures to homologous furrows and lobes. For purely practical reasons, therefore, the furrows and lobes are, following RICHTER & RICHTER (1940, p. 17, fig. 3 A), numbered from back to front. The lobes are lettered "L" (after lobus) and the furrows "S" (after sulcus). In the terminology used previously by BARRANDE (1852, Pl. 1, fig. r), RICHTER & RICHTER (1926, p. 126, fig. 14), and the present writer (1954, p. 55r, fig. 5) the basal (posterior) lobe (furrow) earresponds to Lr (Sr), the middle lobe (furrow) to L2 (S2), and the anterior lobe (furrow) to L3 (S3). These figures in combination with letters L and S ought to be used only if the method of numbering is that applied in the present paper, i. e. from back to front. In this case the letters "p" ( = posterior) or "a" (=an­ terior) after the figures giving the direction of numbering, as suggested by WARBURG (1939, p. s), are superfluous. The terminology of the different types of ventral cephalic sutures used in the present paper earresponds to that of RASETTI (1952). The type with a rostral shield separated by sutures is accordingly called the ptychopariid type. Within this type it is, however, advantageous to distinguish two sub­ types. In the present paper the genera with a broad rostral shield are spoken of as the eu-ptychopariid type (as in Ptychopariidae, Illaenidae, Scutellidae, Cheiruridae etc.). To the genera with a narrow rostral plate (as in Encri­ nuridae, Celmus, Catillicephala, Hystricuridae, Dimeropyge, Dimeropygiella, certain Bathyuridae etc.) the term steno-ptychopariid is applied. The typ e of ventral cephalic sutures where the anterior branches of the facial suture are fused, and no median suture is developed (as in Phacopidae, Nileidae, Leviselfa, Glaphurus, Mesotaphrasis etc.), is called, following RASETTI, the levisellid type, and, when a median suture is developed, the asaphid type. The different types of ventral cephalic sutures referred to in this paper are illustrated in fig. 1. VALDAR JAANUSSON A c Fig. r. Schematic illustrations of the different types of ventraJ cephalic sutures referred to in the present paper. A-eu-ptychopariid type; B-steno-ptychopariid type; C-asaphid type; D-levisellid type. r-rostral shield; m-median suture. Fam. Celmidae n. fam. DIAGNOSIS.-Small, apparently opisthoparian trilobites. Cephalon compara­ tively large, surrounded by a distinct convex horder. Glabella slightly nar­ rowing anteriorly, with two to three pairs of lateral glabellar furrows. L1 comparatively long and well-defined. Occipital furrow present. Rostral shield short (sag.) and narrow (tr.), trapezoidal. Hypostoma with rounded posterior margin, with small pointed posterior wings, and apparently narrow (tr.) and triangular anterior wings. Posterior lobe of the hypostoma well-defined, fair! y convex. 12 thoracic segments in the typ e genus; the width ( tr.) of the segments decreases considerably in posterior direction. Thoracic pleurae of the ridged type, without pleural furrows and facets. Pygidium very small, trapezoidal, apparently consisting of only one tergite; i t has no rachis hut two crescent-shaped elevations near the anterior margin. The type genus has a tuberculate ornamentation. DrscusSION.-The type genus being so far the only genus referable to this family the above diagnosis largely coincides with that of the genus Celmus. As pointed out by FR. ScHMIDT (1907) the genus Crotalurus VoL­ BORTH, 1858 is a junior subjective synonym of Celmus ANGELIN, 1854. In order to solve the question about the taxonomical position of the genus Celmus a large number of genera in some way or other similar to it has to be considered.